3rd generation partnership project (3GPP) standards have defined handover specifications between femtocell. In order to provide handover for user equipment from one femtocell to another, the user equipment may transmit a handover request to a femtocell gateway through a serving femtocell base station. In response to the handover request, the femtocell gateway may perform an access check procedure with a mobile management entity (MME) node. During the access check procedure, the femtocell gateway may determine whether to approve the handover request of the user equipment based on an allowed closed subscriber group list (ACL) of the user equipment.
User equipment may store the ACL. The ACL may be information on femtocell base stations that can be accessed. Such information may be a dosed subscriber group (CSG) identifier of a femtocell base station. For example, when a target femtocell base station is configured in a CSG mode, user equipment may need to have a CSG identifier of a target femtocell base station in order to perform handover from a serving femtocell base station to the target femtocell base station. When the CSG identifier of the target femtocell base station is not included in the ACL of the user equipment, the handover request of the user equipment to the target femtocell base station is typically denied. That is, the target femtocell base station allows only user equipment handover from a serving femtocell base station having the same CSG identifier.
The same CSG identifier may be assigned to femtocells and associated femtocell base stations that belong to the same service provider and the same intranet. That is, each femtocell and each femtocell base station may have different CSG identifiers when the femtocell and the femtocell base stations belong to different service providers and different intranets. Accordingly, handover between femtocell base stations of different service providers or different intranets may not be allowed. A femtocell having different CSG identifiers may be referred to as a “hetero” femtocell,
In general, a building may include a plurality of hetero femtocells of different service providers. For example, a first femtocell with a first femtocell base station may be located at the first floor, a second femtocell with a second femtocell base station may be located at the second floor and the third floor, and a third femtocell with a third femtocell base station may be located at the fifth floor. The first and third femtocells belong to the same intranet so the first and third femtocells have the same CSG identifier. The second femtocell belongs to a different intranet from that of the first and third femtocells. The second femtocell has the different CSG identifier from that of the first and third femtocells. A user with user equipment accessing the first femtocell or the third femtocell frequently may frequently travel between the first floor and the fifth floor. In this case, the user must pass the second femtocell having a CSG identifier different from that of the first femtocell or the third femtocell. In this case, for a handover sequence between the first femtocell and the second femtocell and between the second femtocell and the third femtocell, the user equipment may frequently be disconnected. Accordingly, with such handover, overall communication quality may be seriously degraded in a communication environment including hetero femtocells gathered in such a small area, such as an office building.